Theresa May at her best as she departs Number 10 to be replaced by Boris Johnson

Hundreds of cameras focused on Theresa May as she delivered the final speech of her premiership, in the same spot where she addressed the country when she became prime minister three years ago.

Before stepping through the famous black door of Number 10 for one final time, May enjoyed lunch and said her final thanks to staff, who lined the corridors and could be heard cheering and clapping her inside.

In her final few minutes, ahead of being whisked off to Buckingham Palace to meet the Queen and tender her resignation as prime minister - recommending Boris Johnson as her successor - May stood in front of the lectern placed outside, her husband Philip at her side.

Theresa May looks at her husband Philip as she delivers her final address outside 10 Downing Street. (AAP)

With the nation and the world watching, and every lens and phone on Downing Street pointed in her direction, as May spoke - her speech peppered with the continuous flickering of cameras - she was possibly her most animated and relaxed yet.

With the loud buzzing of a helicopter overhead forcing her to momentarily pause and cast her eyes upwards, May turned to her husband Philip as she thanked him in her speech.

In a moment of rare humour, as she paid tribute to him, a protester shouted "stop Brexit" to which May quipped: "I think the answer to that is, 'I think not'."

Theresa and Philip May wave to the crowd after Mrs May gave her final speech as prime minister. (AAP)Boris Johnson meets with Queen Elizabeth II to become the new Prime Minister of the United Kingdom. (AAP)

Sharing a loving smile between them as her speech drew to a close, they then stood on the sun-drenched steps of Downing Street once more, their arms around each other, waving to the hordes of journalists and photographers crammed into pens.

As the pair then made their way to a waiting car, with no sign of Larry the cat, the staff who had gathered began to clap, with Philip placing a reassuring hand on his wife's back.

Earlier, British MPs gave May a standing ovation as they applauded her out of the House of Commons chamber after her final, at times emotional, appearance as leader.

She appeared to be fighting back tears as she left, stopping to shake hands with the Speaker, John Bercow, on her way out.

"Later today, I will return to the back benches and it will be my first time in 21 years so it is going to be quite a change," May told MPs as her final weekly question session in parliament came to a close.

Theresa May smiles during her final speech in the chamber. (AAP)

Praising the link between MPs and the constituents they represent as "the bedrock of our parliamentary democracy", May's voice quivered as she finished: "That duty to serve my constituents will remain my greatest motivation."

The hour-long session, which her husband Philip watched from the public gallery, saw MPs from across the political divide pay tribute to May's public service and sense of duty despite voicing their disagreement with many of her policies.

Jeremy Corbyn, who tapped his fingers on his knee amid the standing ovation, was no doubt reeling from May's parting shot across the floor earlier in the exchanges.

"As a party leader who has accepted when her time was up, perhaps the time is now for him to do the same," she gibed.

Jeremy Corbyn takes aim at Theresa May in her last PMQs. (AAP)

To add insult to injury, Labour MP Ian Austin later said the "vast majority" on his benches agreed.

Corbyn had earlier paid tribute to May's "sense of public duty" before highlighting increases in poverty, violent crime, NHS waiting times and school class sizes in the past three years, among other things.

May took over as prime minister in the aftermath of the 2016 vote to leave the European Union and is standing down just over three years later having failed to deliver Brexit, her divorce deal with the bloc rejected three times by a deeply divided parliament.